Method and apparatus for recovering indium from waste liquid crystal displays

ABSTRACT

This invention provides a method and apparatus for recovering In in the form of an alloy or a metal simple substance as a valuable material from waste LCD. In the In recovery method and apparatus, there is no need to recover In as indium hydroxide, and In can be recovered as a valuable metal. Accordingly, unlike the case of indium hydroxide, the recovery does not suffer from poor handling, and In can easily be recovered through a filter or the like with significantly improved In recovery. The In recovery method is characterized by comprising crushing waste LCD containing indium tin oxide, dissolving indium tin oxide from the crushed waste LCD with an acid to give an indium compound-containing solution, allowing the solution to flow into a reactor for recovery and, further, adding particles of a metal having a larger ionization tendency than In into the reactor for recovery, fluidizing the metal particles, precipitating In or an In alloy contained in the indium compound-containing solution onto the surface of the metal particles, then separating the precipitated In or In alloy from the metal particles by separation means, and separating and recovering the separated solid In or In alloy from the liquid component.

TECHNICAL FIELD

The present invention relates to a method and apparatus for recoveringindium from waste liquid crystal displays, and more particularly amethod and apparatus for recovering a valuable material, namely indium(In) in the form of an alloy or metal simple substance from waste liquidcrystal televisions, cellular phones or portable game players, or liquidcrystal displays (hereinafter also referred as waste LCD) discharged asrejected products during manufacturing processes.

BACKGROUND ART

For liquid crystal displays (hereinafter also referred as LCDs), indiumtin oxide (ITO) films are used as transparent electrodes. ITO films areformed mainly by sputtering, in which In is used for its target. In is arare metal produced during a zinc refining process and the fear ofdepletion has recently arose. About 300 mg/L of In is contained in awaste LCD, and due to the depleting In, demand exists for recovering Induring recycling process.

In order to meet the above demand, an attempt has been made to recoverIn in waste LCDs. As a technique to do it, an invention is proposed inthe following non-patent document 1. This invention relates to afluidized bed treatment system for LCDs, and this fluidized bedtreatment system for LCDs includes a fluidized bed treatment unit, acyclone, a heat extractor, a high-temperature bag filter, a catalyticfluidized bed and a water washing tower, in which In mechanicallyseparated by silicon sand as a bed material is accumulated in the bedmaterial. However, according to a method using this treatment system,about 60% of In is accumulated in the bed material and the residual iscaught by a bag filter, so that an overall indium recovery rate is about60% and a low recovery rate of only about 60% was achieved.

Non-patent document 1: April 2002 Issue of Monthly Display, Pages 36-46.

In order to increase such a low recovery rate associated with a dryprocessing as described above, there has been developed a wetprocessing. For example, the following patent document 1 discloses amethod that includes dissolving ITO in acid such as nitric acid orhydrochloric acid, then removing impurities such as Sn by sedimentation,and then adding ammonia thereto for neutralization, thus allowing indiumto be recovered as indium hydroxide.

Patent document 1: Japanese Patent Application Laid-open No. 2000-128531

However, according to the method of the above wet processing,filterability of indium hydroxide produced by the treatment is poor andhence it takes a long time for operation, as well as there is a problemin that the characteristics of indium hydroxide produced byneutralization or the like are changed.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present invention has been conceived to solve the above problems. Itis an object of the present invention to provide an In recovering methodand apparatus that is capable of recovering In as a valuable materialwithout the necessity to recover it in the form of indium hydroxideunlike the conventional method, thereby being capable of preventing poorhandling during recovering unlike indium hydroxide, easily recovering Inby filter or the like and thus remarkably improving the In recoveringrate.

Means to Solve the Problem

The present invention has been made in order to solve the aboveproblems. A method of recovering indium from waste liquid crystaldisplays, of claim 1 is characterized in that it comprises: crushingwaste liquid crystal displays that contain indium tin oxide; dissolvingthe indium tin oxide from the waste liquid crystal displays by usingacid, thereby producing an indium composition-containing solution;flowing the same into a recovering reactor while adding metal particlesof a metal having an ionization tendency larger than indium into therecovering reactor; fluidizing the metal particles; depositing indium orindium alloy contained in the indium composition-containing solutiononto the surface of the metal particles; then separating the depositedindium or indium alloy from the metal particles by a separating means;and isolating and recovering the separated indium or indium alloy in asolidified form from the liquid component.

In claim 2, a method of recovering indium from waste liquid crystaldisplays according to claim 1 is characterized in that the metalparticles of the metal having an ionization tendency larger than indiumare any one of zinc particles and aluminium particles. In claim 3, amethod of recovering indium from waste liquid crystal displays accordingto any one of claims 1 and 2 is characterized in that the separatingmeans for separating the indium or indium alloy deposited onto the metalparticles comprises any one of a vibrating means for vibrating the metalparticles by ultrasonic waves and a stirring means for stirring themetal particles by electromagnet and thereby making the metal particlescollide with one another.

In claim 4, a method of recovering indium from waste liquid crystaldisplays according to any one of claims 1 to 3 is characterized in thatthe indium composition-containing solution produced by dissolving theindium tin oxide from the waste liquid crystal displays is flown into animpurity removing reactor prior to the flowing of the indiumcomposition-containing solution into the recovering reactor; metalparticles of a metal having an ionization tendency larger than animpurity metal other than the indium in the indiumcomposition-containing solution are added into the impurity removingreactor, thereby fluidizing the metal particles and depositing theimpurity metal on the surface of the metal particles; and then thedeposited impurity metal is separated and removed from the metalparticles by the separating means.

In claim 5, a method of recovering indium from waste liquid crystaldisplays according to claim 4 is characterized in that the separatingmeans for separating the impurity metal deposited onto the metalparticles comprises any one of a vibrating means for vibrating the metalparticles by ultrasonic waves and a stirring means for stirring themetal particles by electromagnet and thereby making the metal particlescollide with one another. In claim 6, a method of recovering indium fromwaste liquid crystal displays according to any one of claims 4 and 5 ischaracterized in that the impurity metal is tin. In claim 7, a method ofrecovering indium from waste liquid crystal displays according to anyone of claims 4 to 6 is characterized in that the metal particles of themetal having an ionization tendency larger than the impurity metal areiron particles. In claim 8, a method of recovering indium from wasteliquid crystal displays according to claim 7 is characterized in thatalkali is added into the indium composition-containing solution with theimpurity metal removed therefrom, and iron is removed in the form ofhydroxide by sedimentation. A method of recovering indium from wasteliquid crystal displays of claim 9 is characterized in that itcomprises: crushing waste liquid crystal liquid displays that containindium tin oxide; dissolving the indium tin oxide from the waste liquidcrystal displays by using acid, while the crushed waste liquid crystaldisplays are kept placed in a bag, thereby producing an indiumcomposition-containing solution; and washing and neutralizing the wasteliquid crystal displays placed in the bag and then drying the same.

An apparatus for recovering indium from waste liquid crystal displays ofclaim 10 is characterized in that it comprises: crusher for crushingwaste liquid crystal displays that contain indium tin oxide; an indiumdissolution device for dissolving the indium tin oxide from the wasteliquid crystal displays, thereby producing an indiumcomposition-containing solution; a recovering reactor for allowing theindium composition-containing solution produced by the indiumdissolution device to flow into the recovering reactor while allowingmetal particles of a metal having an ionization tendency larger thanindium to be added into the recovering reactor, thereby carrying out ametal deposition reaction that deposits indium or indium alloy onto themetal particles; a separating means for separating the deposited indiumor indium alloy from the metal particles to recover the same; and anisolating means for isolating the separated indium or indium alloy in asolidified form from the liquid component.

In claim 11, an apparatus for recovering indium from waste liquidcrystal displays according to claim 10 is characterized in that themetal particles of the metal having an ionization tendency larger thanindium are any one of zinc particles and aluminium particles. In claim12, an apparatus for recovering indium from waste liquid crystaldisplays according to any one of claims 10 and 11 is characterized inthat the separating means for separating the indium or indium alloydeposited onto the metal particles comprises any one of a vibratingmeans for vibrating the metal particles by ultrasonic waves and astirring means for stirring the metal particles by electromagnet andthereby making the metal particles collide with one another.

In claim 13, an apparatus for recovering indium from waste liquidcrystal displays according to any one of claims 10 to 12 ischaracterized in that an impurity removing reactor is disposed on theupstream side of the recovering reactor, said impurity removing reactorbeing arranged to flow the indium composition-containing solutionproduced by the indium dissolution device into the impurity removingreactor; add metal particles of a metal having an ionization tendencylarger than an impurity metal other than the indium in the indiumcomposition-containing solution into the impurity removing reactor,thereby fluidizing the metal particles and depositing the impurity metalonto the surface of the metal particles; and have a means of separatingand removing the deposited impurity metal from the metal particles.

In claim 14, an apparatus for recovering indium from waste liquidcrystal displays according to claim 13, is characterized in that theseparating means for separating the impurity metal deposited onto themetal particles comprises any one of a vibrating means for vibrating themetal particles by ultrasonic waves and a stirring means for stirringthe metal particles by electromagnet and thereby making the metalparticles collide with one another. In claim 15, an apparatus forrecovering indium from waste liquid crystal displays according to anyone of claims 13 and 14 is characterized in that the impurity metal istin.

In claim 16, an apparatus for recovering indium from waste liquidcrystal displays according to any one of claims 13 to 15 ischaracterized in that the metal particles of the metal having anionization tendency larger than the impurity metal are iron particles.In claim 17, an apparatus for recovering indium from waste liquidcrystal displays according to claim 16 is characterized in that alkaliis added into the indium composition-containing solution with theimpurity metal removed therefrom, and iron is removed in the form ofhydroxide by sedimentation.

ADVANTAGES OF THE INVENTION

As mentioned above, according to the present invention, there isprovided a method of recovering indium from waste liquid crystaldisplays, which comprises crushing waste liquid crystal displays (LCDs)that contain indium tin oxide; dissolving the indium tin oxide from thewaste LCDs, thereby producing an indium composition-containing solution;flowing the same into a recovering reactor while adding metal particlesof a metal having an ionization tendency larger than indium (In) intothe recovering reactor; fluidizing the metal particles; depositing In orIn alloy contained in the indium composition-containing solution ontothe surface of the metal particles; then separating the deposited In orIn alloy from the metal particles by a separating means; and isolatingand recovering the separated In or In alloy in a solidified form fromthe liquid component. With this method, ITO can be easily andefficiently dissolve from waste LCDs. By combining a cementationreaction utilizing the ionization tendency with the separatingtechnique, and specifically, using metal particles in recovering In froma solution with In dissolved therein, the overall surface area of ametal for metal deposition reaction is increased, thereby improving thedeposition reaction rate, and furthermore, by separating a depositedmetal, which has been grown to some extent, by the separating means, afresh surface of the metal is constantly exposed so that the reactionrate can be kept constant. Whereby, there is an advantage in that the Inrecovering rate from waste LCDs can be remarkably improved, evencompared with any of the conventional drying type and the wet type. Inthe present invention, with respect to the In recovering rate fromwastewater, a high recovering rate, namely 80% or higher was achieved.

Unlike the conventional wet processing, In is not necessarily recoveredin the form of indium hydroxide, while In can be recovered as a valuablemetal. Therefore, unlike the case of indium hydroxide, there areadvantages in that the recovery does not suffer from poor handling andIn can be easily recovered by filter or the like.

Furthermore, when the impurity removing reactor that causes a metaldeposition reaction in the same manner as the recovering reactor isdisposed on the upstream side of the recovering reactor, it is possibleto appropriately remove Sn or the like as an impurity metal by addingmetal particles such as iron (Fe) having an ionization tendency largerthan that of the impurity metal other than In contained in an indiumcomposition-containing solution with indium tin oxide dissolved fromwaste LCDs, such as tin (Sn), thereby fluidizing the indiumcomposition-containing solution, hence depositing the impurity metalsuch as Sn contained in the wastewater onto the metal particles, andthen separating the deposited impurity metal from the metal particles bythe separating means.

Thus, since the wastewater having the impurity metals other than In,such as Sn previously removed therefrom can be supplied into therecovering reactor, there is an advantage in that the purity of Inrecovered by the recovering reactor can be further improved.Specifically, In could be recovered at a purity of 95% or higher bydisposing the impurity removing reactor on the upstream side of therecovering reactor.

When impurity metals have been removed by using such impurity removingreactor, ions of the added metals, such as the aforesaid iron, areeluted. However, by providing the sedimentation removing device disposedon the downstream side, which allows metals such as iron to beprecipitated in the form of hydroxide by adding alkali, the hydroxide ofiron and the like can be previously removed before the wastewater issupplied into the recovering reactor. In this case, when pH isincreased, a precipitation of indium hydroxide may be generated.However, the precipitation generation rate of iron hydroxide is muchhigher than that of indium hydroxide. Therefore, the retention timecontrol in the sedimentation removing device can prevent generation ofindium hydroxide and hence supply In to the next recovering reactoralmost without the loss of In. In addition, even if a part of In existsin the form of indium hydroxide in a solution, the In recovering rate isnot deteriorated since the indium hydroxide is again dissolved byadjusting pH in the next recovering reactor.

When an In elution treatment by acid, a washing and neutralizationtreatment, and a drying treatment are carried out while waste LCDs arekept placed in a bag, there is an advantage in that a simplified processcan be achieved by continuously placing waste LCDs finely crushed in thewaste LCD crushing step in the bag throughout the process. In addition,since there is no need to handle powdery waste LCDs received from thewaste LCD crushing step, in which they are finely crushed, it is notdifficult to handle them.

As mentioned above, the present invention can provide an In recoveringmethod with a high recovering rate. Therefore, even when the recoveringrecycle of LCDs becomes required by a home appliance recycling law,there is an actual advantage in that the present invention can beapplied as an In recovering method in a recycling process in a recycleplant of liquid crystal displays.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of an apparatus for recovering Infrom waste LCDs according to one embodiment.

FIG. 2 is a schematic front view of an impurity removing reactor orrecovering reactor in the In recovering apparatus.

FIG. 3 is a schematic front view of an impurity removing reactor orrecovering reactor of another embodiment.

FIG. 4 is a schematic front view of an impurity removing reactor orrecovering reactor of still another embodiment.

FIG. 5 is a schematic plan view of a slide board equipped withelectromagnets for use in the embodiment of FIG. 4.

FIG. 6 is a schematic block diagram illustrating an In recoveringapparatus of yet another embodiment.

FIG. 7 is a schematic cross sectional view of an elution treatmentdevice in the In recovering apparatus.

FIG. 8 is a schematic explanatory view of an apparatus used in Examples.

DESCRIPTION OF THE REFERENCE NUMERALS

2: impurity removing reactor, 3: sedimentation removing device, 4:recovering reactor

Best Mode for Carrying Out the Invention

Now, the description will be hereinafter made for embodiments of thepresent invention with reference to the drawings attached hereto.

Embodiment 1

An apparatus for recovering indium from waste LCDs, of this embodimentincludes, as illustrated in FIG. 1, an indium dissolution device(hereinafter referred also as an In dissolution device) 1 for dissolvingITO from waste LCDs by using hydrochloric acid; an impurity removingreactor 2 for removing impurity metals other than In by adding ironparticles (Fe particles) into an indium compound-containing solutionthat contains In dissolved at the In dissolution device 1; a depositremoving device 3 for removing the Fe particles in the form of hydroxideof iron (Fe) by sedimentation from wastewater with impurity metalsremoved therefrom at the impurity removing reactor 2; and a recoveringreactor 4 for recovering In from the wastewater with the Fe hydroxideremoved therefrom at the deposit removing device 3. Although noillustration is made, a crusher for crushing waste LCDs is disposed onthe upstream side of the In dissolution device 1. By the crushing ismeant in the present invention crushing waste LCDs, and accordingly, thesize of crushed pieces is not the matter. For example, the crushing ismeant to also contain pulverizing which is generally recognized asreduction to very small pieces by crushing, grinding or the like.

The In dissolution device 1 is to produce an indiumcomposition-containing solution by dissolving In from crushed waste LCDsby hydrochloric acid (aqueous hydrochloric acid solution). An indiumcomposition-containing solution is prepared to contain 100-300 mg/L ofIn. Furthermore, this indium composition-containing solution is preparedto have a hydrochloric acid concentration of 20% and allow thehydrochloric acid to have a pH of 1.5.

The impurity removing reactor 2 is to remove Sn as an impurity from theindium composition-containing solution, and arranged with a verticallylong reactor body 5, as illustrated in FIG. 2. This reactor body 5 is,as illustrated in this Figure, made up of a reactor upper portion 6, areactor intermediate portion 7 and a reactor lower portion 8, in whichthese portions are interconnected to each other with interconnectionportions 9, 10. The reactor upper portion 6, the reactor intermediateportion 7 and the reactor lower portion 8 each have a uniform width,while the reactor upper section 6 is larger in cross sectional area thanthe reactor intermediate section 7 and the reactor intermediate section7 is larger in cross sectional area than the reactor lower section 8.Thus, the cross sectional area of the reactor body 5 as a wholediscontinuously increases towards the upper side. The interconnectionportions 9, 10 each have a tapered shape with the width increasingtowards the upper side.

Disposed on the lower side of the reactor lower section 8 is an inflowchamber 11 of a substantially conical shape for allowing inflow of anindium composition-containing solution to be treated, and disposed onthe lower side of the inflow chamber 11 is an inflow pipe 12. Althoughnot illustrated, a check valve is disposed in the inflow pipe 12.Disposed on the upper side of the reactor upper section 6 is an upperchamber 13 with an outflow pipe 14 attached to a lateral side thereoffor allowing Sn as an impurity metal to be deposited onto metalparticles (Fe particles) and discharged therethrough. The upper chamber13 is a section for discharging Sn together with Fe particles by suchoutflow pipe 14, as well as is a section for allowing Fe particles to bethrown therein, in which Fe particles cause a so-called cementationreaction (metal deposition reaction) based on the difference inionization tendency between Fe and Sn as an impurity to be removed. Inpractice, the cementation reaction of Fe and Sn takes place in theentire reactor body 1.

It is so structured that the indium composition-containing solutionflown in through the inflow pipe 12 allows its wastewater to form afluidized bed of Fe particles while moving up vertically, until itreaches the outflow pipe 14. Ultrasonic oscillation members 15 a, 15 b,15 c as a means of removing Sn, which is an impurity metal contained inthe indium composition-containing solution and deposited onto the Feparticles by the cementation reaction, are provided respectively in thereactor upper section 6, the reactor intermediate section 7 and thereactor lower section 8.

In this embodiment, Fe particles are used as metal particles to bethrown in. Metal particles such as Fe particles having an averageparticle diameter of 0.1 to 8 mm are preferably used. In thisembodiment, particles having an average particle diameter of about 3 mmare used. The average particle diameter is measured by an image analysismethod or a screening test according to JIS Z 8801.

The sedimentation removing device 3 is to remove the Fe particles ashydroxide by sedimentation. The precipitate removal of hydroxide isachieved by adding alkali (alkali solution) such as sodium hydrate. ThepH of wastewater within the sedimentation removing device 3 is adjustedto 8 to 9.

The recovering reactor 4 is to remove Sn as an impurity as describedabove, and recover In from an indium composition-containing solutionwith Fe removed in the form of hydroxide by sedimentation, and has thesame structure as that of the impurity removing reactor 2. That is, asillustrated in FIG. 2, the recovering reactor 4 includes the reactorbody 5 made up of the reactor upper section 6, the reactor intermediatesection 7 and the reactor lower section 8 interconnected via theinterconnection portions 9, 10. The pH within the recovering reactor 4is adjusted to 1.5 or lower.

The recovering reactor 4 is the same as the impurity removing reactor 2in structure in that the inflow chamber 11, the inflow pipe 12, theupper chamber 13 and the outflow pipe 14 are disposed, and theultrasonic oscillation members 15 a, 15 b, 15 c are disposedrespectively in the reactor upper section 6, the reactor intermediatesection 7 and the reactor lower section 8.

Now, the description will be made for a method of recovering In fromwaste LCDs by an apparatus having the above structure for recovering Infrom waste LCDs. First, waste LCDs are crushed by a crusher (notillustrated) and crushed waste LCDs are supplied into the In dissolutiondevice 1. Then, hydrochloric acid (aqueous hydrochloric acid solution)is added into this In dissolution device 1 to elute In from the wasteLCDs by the hydrochloric acid, and thus an indium composition-containingsolution, which contains 100 to 300 mg/L of In is produced within the Indissolution device 1.

Then, this indium composition-containing solution is supplied into theimpurity removing reactor 2. The indium composition-containing solutionsupplied into the impurity removing reactor 2 flows through the inflowpipe 12 of the impurity removing reactor 2 into the reactor body 5 viathe inflow chamber 11. On the other hand, metal particles (Fe particles)for causing a cementation reaction are thrown into the reactor body 5through the upper chamber 13. In the reactor body 5, the indiumcomposition-containing solution flown in moves up in a verticaldirection, while this indium composition-containing solution and the Feparticles thrown in through the upper chamber 13 are brought intofluidized state to form a fluidized bed.

Then, based on the difference in ionization tendency between impuritymetals other than In contained in the indium composition-containingsolution, more specifically Sn, and Fe as metal particles thrown in, aso-called cementation reaction is caused. Giving a detailed explanationof this, the reduction reactions of the respective metal ions arerepresented in the following expressions, in which the standardelectrode potentials (E°) of the respective metal ions are indicated.

$\begin{matrix}{{{Fe}^{2 +} + {2e}}->{{Fe} - {0.44\mspace{14mu} V}}} & (1) \\{{{Sn}^{2 +} + {2e}}->{{Sn} - {0.14\mspace{14mu} V}}} & (2)\end{matrix}$

As being apparent from the above (1) and (2), the standard electrodepotential of Fe²⁺ is smaller than that of Sn²⁺. In other words, Fe islarger than Sn in ionization tendency. Therefore, under the abovefluidized state, Fe having a large ionization tendency turns to be Fe²⁺(a reversed reaction of the above (1) expression) and is eluted into theindium composition-containing solution, while Sn²⁺ contained in theindium composition-containing solution turns to be Sn and is depositedonto the surface of Fe particles.

Then, after Sn has been deposited onto the surface of Fe particles bysuch cementation reaction, the ultrasonic oscillation members 15 a, 15b, 15 c are actuated. By the actuation of the ultrasonic oscillationmembers 15 a, 15 b, 15 c, ultrasonic waves emitted therefrom applyvibration force and stirring force to Fe particles with the Sn depositedthereon so that deposited Sn is forcibly separated from the Feparticles.

The thus separated Sn is discharged to the outside of the reactor body 5from the upper chamber 13 through the outflow pipe 14, and hence removedfrom the indium composition-containing solution. In this case, in thisembodiment, metal (Fe) thrown in for removing impurity metals is in aparticulate form, and therefore the surface area of the metal (Fe) forcausing the cementation reaction is increased as compared with a case,in which, for example, iron pieces are thrown in. Hence, the rate of thedeposition reaction of Sn is improved. Then, after it has been confirmedthat the deposited metal was grown to some extent, a fresh surface ofthe metal (surface of Fe particles) is constantly exposed by the forcedseparation by the above ultrasonic vibration, thereby enabling thereaction rate to be kept constant.

Metal particles of Fe are fluidized in the reactor body 5 and Fe²⁺ iseluted by the above cementation reaction, and therefore the particlesize in the initial stage of the throwing-in of metal particles, whichhave been thrown into the upper chamber 13, necessarily decreases as thetime elapses. As a result, since wastewater moves upward within thereactor body 5 at substantially the same upflow rate under ordinalcircumstances, metal particles having the particle size decreasing asthey advance towards the upper side may unintentionally overflow fromthe reactor body 5.

However, in this embodiment, since the cross sectional area of thereactor body 5 is discontinuously increased towards the upper side, theupflow rate of the wastewater within the reactor body 5 is graduallydecreased and hence metal particles with the particle size having beendecreased by the above cementation reaction become more likely to beretained within the reactor body 5 without unintentional overflow, in anupper portion of the reactor body 5, which portion having an increasingcross sectional area.

Since an indium composition-containing solution, which flows in throughthe lower side of the reactor body 5, allows a subject metal such as Snto be deposited onto metal particles of Fe by the cementation reactionwhen it passes the inside of the reactor body 5, the concentration ofmetal impurity in the indium composition-containing solution decreasesas the indium composition-containing solution moves towards the upperside of the reactor body 5.

However, in this embodiment, it is confirmed that the metal particlesbecome finer as they are closer to the upper side of the reactor body 5,and the number of metal particles is increased as the upflow rate of theindium composition-containing solution is gradually decreased. Thus, theoverall surface area of the metal particles is increased as they arecloser to the upper side of the reactor body 5. As a result, the rate ofthe cementation reaction (efficiency of the impurity metal deposition)is improved. Thus, Ni and Sn as impurity metals can be efficientlyremoved even in an upper portion of the reactor body 5, in which theconcentration of impurity metals is lowered.

Then, the indium composition-containing solution with Sn removedtherefrom is supplied into the deposit removing device 3. Alkali(alkaline solution), such as sodium hydrate, is added into the depositremoving device 3. Whereby, hydroxides of Fe and solid products ofindium hydroxide are generated. Specifically, in the impurity removingreactor 2, Sn is deposited onto the Fe particles and removed by thecementation reaction, while Fe ions (Fe²⁺) are eluted into the indiumcomposition-containing solution. Accordingly, it is necessary to removethe Fe²⁺ as well before the indium composition-containing solution issupplied into the recovering reactor 4 disposed on the downstream side.In this regard, although hydroxides of Fe and solid products of indiumhydroxide are generated by the addition of alkali, the hydroxides of Feare easily removed in the sedimentation removing device 3, which issimilar to a coagulation sedimentation tank, by controlling the time forwhich the subject water is retained in the sedimentation removing device3, since the hydroxides of Fe generate a deposit at a much greater ratethan indium hydroxide.

Then, the indium composition-containing solution with the hydroxides ofFe removed is adjusted to a pH of 1.5 or lower, thereby causing theindium hydroxide to be again dissolved therein, and then is suppliedinto the recovering reactor 4. The indium composition-containingsolution supplied into the recovering reactor 4 is flown into thereactor body 5 from the inflow pipe 12 via the inflow chamber 11, in thesame manner as in the case of the impurity removing reactor 2. On theother hand, metal particles (Zn particles or Al particles) for causingthe cementation reaction are thrown into the reactor body 5 from theupper chamber 13. In the same manner as in the case of the impurityremoving reactor 2, an indium composition-containing solution flown inthe reactor body 5 moves upward so that metal particles thrown in fromthe upper chamber 13 are brought into fluidized state.

Then, a so-called cementation reaction is caused based on the differencein ionization tendency between In in the indium composition-containingsolution to be recovered and Zn or Al as metal particles thrown in. Thereduction reactions of the respective metal ions are represented in thefollowing expressions, in which the standard electrode potentials (E°)of the respective metal ions are indicated.

$\begin{matrix}{{{In}^{3 +}3e}->{{In} - {0.34\mspace{14mu} V}}} & (3) \\{{{Zn}^{2 +} + {2e}}->{{Zn} - {0.76\mspace{14mu} V}}} & (4) \\{{{Al}^{3} + {3e}}->{{Al} - {1.66\mspace{14mu} V}}} & (5)\end{matrix}$

As being apparent from the above (3) to (5), the standard electrodepotential of Zn²⁺ or Al³⁺ is smaller than that of In³⁺. In other words,Zn or Al is larger than In in ionization tendency. Therefore, under theabove fluidized state, Zn or Al having a large ionization tendency turnsto be Zn²⁺ or Al³⁺ (a reversed reaction of the above (4) and (5)expressions) and is eluted into the indium composition-containingsolution, while In³⁺ contained in the indium composition-containingsolution turns to be In and is deposited onto the surface of Zn or Alparticles.

Then, after In has been deposited onto the surface of Zn or Al particlesby such a cementation reaction, the ultrasonic oscillation members 15 a,15 b, 15 c are actuated. By the actuation of the ultrasonic oscillationmembers 15 a, 15 b, 15 c, ultrasonic waves emitted therefrom applyvibration force and stirring force to Zn or Al particles with the Inseparated therefrom, and thereby precipitated In is forcibly separatedfrom the Zn or Al particles.

The thus separated In is discharged to the outside of the reactor body 5from the upper chamber 13 through the outflow pipe 14, and thereby In isrecovered as a valuable metal. In this case, in this embodiment, sinceZn or Al to be thrown in is in a particulate form in the same manner asin the case of iron of the impurity removing reactor 2, and thereforethe surface area of the metal for causing the cementation reaction isincreased and hence the rate of the precipitation reaction of In isimproved.

Then, after it has been confirmed that the precipitated metal was grownto some extent, a fresh surface of the Zn or Al particles is constantlyexposed by the forced separation by the above supersonic vibration,thereby enabling the reaction rate to be kept constant.

Zn²⁺ or Al³⁺ is eluted from Zn or Al particles by the cementationreaction, and therefore the particle size of Zn or Al thrown into theupper chamber 13 in the initial stage of the throwing-in necessarilydecreases as the time elapses. As a result, since the indiumcomposition-containing solution moves upward within the reactor body 5at substantially the same upflow rate under ordinal circumstances, Zn orAl particles having the particle size decreasing as they advance towardsthe upper side may unintentionally overflow from the reactor body 5.

However, in this embodiment, since the cross sectional area of thereactor body 5 is discontinuously increased towards the upper side, theupflow rate of the indium composition-containing solution within thereactor body 5 is gradually decreased and hence metal particles with theparticle size having been decreased by the above cementation reactionbecome more likely to be retained within the reactor body 5 withoutunintentional overflow, in an upper portion of the reactor body 5, whichportion having an increasing cross sectional area.

Since an indium composition-containing solution, which flows in throughthe lower side of the reactor body 5, allows In as a subject to bedeposited onto Zn or Al particles by the cementation reaction when itpasses the inside of the reactor body 5, the concentration of In in theindium composition-containing solution decreases as the indiumcomposition-containing solution moves towards the upper side of thereactor body 5.

However, in this embodiment, it is confirmed that the Zn or Al particlesbecome finer as they are closer to the upper side of the reactor body 5,and the number of Zn or Al particles is increased as the upflow rate ofthe indium composition-containing solution is gradually decreased. Thus,the overall surface area of the Zn or Al particles is increased as theyare closer to the upper side of the reactor body 5. As a result, therate of the cementation reaction (efficiency of the In deposition) isimproved. Thus, In as a subject to be recovered can be more efficientlyremoved from the indium composition-containing solution even in an upperportion of the reactor body 5, in which portion the concentration of Inis lowered.

Embodiment 2

This embodiment is different from Embodiment 1 in structure of theimpurity removing reactor 2 and the recovering reactor 4. Specifically,in this embodiment, as illustrated in FIG. 3, the entire circumferentialwall of the reactor body 5 is tapered upward, and the cross sectionalarea of the reactor body 5 is continuously increased. This embodiment isdifferent in this respect from Embodiment 1, in which the crosssectional area of the reactor body 5 is discontinuously increasedtowards the upper side.

Since the cross sectional area is increased towards the upper side notdiscontinuously but continuously, the reactor body 5 is not arrangedwith separate sections, such as the reactor upper section 6, the reactorintermediate section 7 and the reactor lower section 8.

However, this embodiment is the same as Embodiment 2 in that theultrasonic oscillation members 15 a, 15 b, 15 c are provided at threepoints on the way from the upper portion to the lower portion, of thereactor body 5. Therefore, in this embodiment, there is provided anadvantage in that Sn as an impurity metal, which is deposited onto metalparticles and must be removed, or In as a metal to be recovered, can beforcibly separated by ultrasonic waves emitted from the ultrasonicoscillation members 15 a, 15 b, 15 c, in the same manner as inEmbodiment 1.

Although there is a difference between the discontinuous formation andcontinuous formation, of the cross sectional area, this embodiment isthe same as Embodiment 2 in that the cross sectional area is increasedtowards the upper side. Therefore, in this embodiment, there areprovided an advantage in that metal fine particles having a reducedparticle size are retained in the upper portion of the reactor body 5,thereby preventing unintentional overflow, and an advantage in that asubject metal can be efficiently removed or recovered in an upperportion of the reactor body 5, in which portion the concentration of thesubject metal is low.

Embodiment 3

In this embodiment, as a means for separating a deposited metal frommetal particles, a stirring means by using electromagnet is employed inplace of a vibrating means by ultrasonic waves emitted by the ultrasonicoscillation members of Embodiments 1 and 2. Specifically, in thisembodiment, a slide board 17 equipped with electromagnets 16 asillustrated in FIG. 5 is mounted on guide rails 18 so as to be able tobe moved upward and downward, which guide rails being disposed on thelateral sides of the reactor body 5 having a rectangular horizontalcross section, as illustrated in FIG. 4. The slide board 17 has a space19 at a center portion, as illustrated in FIG. 5, and the reactor body 5is placed in the space 19 so that the reactor body 5 is surrounded bythe slide board 17. Metal particles used in this embodiment are amagnetic substance such as iron or the like.

As illustrated by the arrow 20 of FIG. 4, the slide board 17 is movedalternatively upward and downward to stir metal particles within thereactor body 5, while making a number of the metal particles collidewith one another, thereby forcibly separating the deposited metal fromthe metal particles. Although there is a difference in means forseparating a deposited metal from metal particles, in this embodiment aswell, the deposited metal is appropriately separated from the metalparticles so that an impurity metal can be appropriately removed or Inas a valuable metal can be appropriately recovered.

Embodiment 4

The description will be made for this embodiment by taking a case inwhich an In elution treatment by acid, a washing and neutralizationtreatment, and a drying treatment are carried out while waste LCDs arekept placed in a bag. An apparatus for recovering indium from waste LCDsin this embodiment includes an elution treatment device 25, a washingand neutralizing device 26 and a drying device 27, as illustrated inFIG. 6. The elution treatment device 25 includes an elution treatmentcontainer 22, such as a tank made of FRP, as illustrated in FIG. 7. Thiselution treatment container 22 is sized to accommodate waste LCDs placedin a bag 21 such as a flexible container bag, made of resin or cloth. Aporous plate 23 and a porous-plate supporting member 24 are disposed ona lower portion of the elution treatment container 22. The bag 21 isstructured to be supported on this porous plate 23.

While waste LCDs crushed by a crusher or the like are kept placed in thebag 21, a hydrochloric acid solution for In dissolution and extractionis circulated so that In is eluted from the waste LCDs when thehydrochloric acid solution passes through a waste LCD layer 28. That is,indium tin oxide is dissolved from waste LCDs by using hydrochloric acidto produce an indium composition-containing solution.

On the other hand, the waste LCDs, which have been subjected to thedissolution and extraction treatment, are moved to the next washing andneutralizing device 26 while being still kept placed in the bag 21, andare placed in the washing and neutralizing device 26, at which they aresubjected to the washing and neutralization treatment. The movement fromthe elution treatment device 25 to the washing and neutralizing device26 is achieved by utilizing a hoist or the like. In the same manner asthe In dissolution treatment, the washing is made by circulating waterand the neutralization is made by circulating an alkaline solution. Thecirculation treatment may be made by either downward flow or upward flowof these circulating fluids. The waste LCDs, which have been subjectedto the washing and neutralization treatment, are moved to the dryingdevice 27 while being still kept placed in the bag. The drying device 27is to carry out a drying treatment by, for example, flash drying, but itis possible to carry out a drying treatment by, for example, a dryingmethod such as solar drying without using this drying device 27. Thewaste LCDs, which have been subjected to the drying treatment, areshipped to tile-making plants, glass-making plates or the like asrecycled materials, while being still kept placed in the bag 21.

In this embodiment, a simplified process can be achieved by continuouslyplacing waste LCDs finely crushed in the waste LCD crushing step in thebag 21 throughout the process. In addition, since there is no need tohandle powdery waste LCDs received from the waste LCD crushing step, inwhich they are finely crushed, it is not difficult to handle them.

The bag 21 may be mesh (porous) with such a size of openings not toallow waste LCDs to fall therethrough, and therefore a cloth bag or thelike is satisfactorily used for it. The bag may be entirely porous tosuch an extent as to allow a hydrochloric acid solution to passtherethrough, or may be porous only for a bottom surface. In anyarrangement, tight contact between the bag 21 and the elution treatmentcontainer 22 can be achieved by the weight of the waste LCDs in the bag21 upon placing the bag 21 on the porous plate 23 within the elutiontreatment container 22, so that a hydrochloric acid passes through awaste LCD layer and moves to a bottom portion of the elution treatmentcontainer 22 from the bottom surface of the bag 21 via the porous plate23, thereby enabling In to be dissolved and extracted from the wasteLCDs by the circulation treatment.

Other Embodiments

The description was made for the above embodiments by taking the case inwhich Sn is removed as an impurity metal other than In contained in anindium composition-containing solution produced from waste LCDs bydissolving ITO by using a hydrochloric acid, while it is possible toremove a metal other than Sn. In such a case, it is possible to addmetal particles other than Fe.

Also, the description was made for the above embodiments by taking thecase in which In is precipitated onto metal particles and theprecipitated In is separated from the metal particles, while it is notnecessarily limit to a metal simple substance such as In. The presentinvention is applicable to the case in which an alloy of In and othermetals, or an In alloy is precipitated onto metal particles and theprecipitated In alloy is separated from the metal particles.

In the above embodiments, as acid for dissolving ITO from waste LCDs,hydrochloric acid is used, while it is not necessary to limit the typeof the acid to hydrochloric acid. For example, it is possible to usesulfuric acid, nitric acid or the like, or possible to use a mixed acid.

In the above embodiments, it is possible to provide a preferable effectas mentioned above by providing the impurity removing reactor 2 of theabove type, while it is not essential for the present invention toprovide the impurity removing reactor 2. Furthermore, although the aboveembodiments were described by taking the case in which Zn or Alparticles are added to recover In, the metal particles to be added to arecovering reactor are not necessarily limited to Zn or Al particles ofthe above embodiments, and it is essential to use a metal having anionization tendency larger than In.

In the above embodiments, the particle diameter of the metal particlesis about 3 mm. This particle size of metal particles is not necessarilylimited to that of the above embodiments, and is preferably 0.1 to 8 mm.When it is smaller than 0.1 mm, an appropriate cementation reaction isnot necessarily caused, and the deposited metal separated from the metalparticles may not be easily recovered. When it exceeds 8 mm, the numberof metal particles that can be retained in the reactor body may belowered, with the result that the overall surface area of the metalparticles is reduced, hence the efficiency of the deposition reactionmay be deteriorated, and, in addition, metals other than valuable metalsor impurity metals to be recovered may be deposited on the metalparticles.

Furthermore, in Embodiments 1 and 2, the cross sectional area of thereactor body 5 is increased as it advances towards the upper side toproduce the above preferable effect, while it is not essential for thepresent invention to form the reactor body 5 into such a shape. Stillfurthermore, a means for separating a deposited metal from metalparticles is not necessarily achieved by a means by ultrasonic waves ofEmbodiments 1 and 2 or a means by the electromagnet of Embodiment 3,while it may be achieved by any other means.

Example

In dissolution and extraction treatments for In recovering were carriedout by an apparatus as illustrated in FIG. 8, using 1%, 3% and 10%hydrochloric acid solutions. In FIG. 8, reference numerals 28 representsa waste LCD layer described in FIG. 7 as well; 29 represents a tubepump; 30 represents hydrochloric acid; 31 represents a resin container;and 32 represents a mesh basket, respectively. According to theanalysis, the waste LCDs contained 400 mg/kg of In. The elutiontreatment was made by retaining 24 kg of waste LCDs in a cotton bag;placing the bag in the resin container 31 that is placed on the meshbasket installed within a 100-L resin container, as illustrated in FIG.8, and that has a number of openings in a bottom surface; throwing 14 Lof hydrochloric acid thereinto; and circulating it at room temperatureby using the tube pump 29. In order to prevent change in concentrationand amount of hydrochloric acid due to evaporation of water during theelution treatment, a gasket is disposed in a lid of the 100-L resincontainer, and an insertion/taking-out portion of the tube pump 29 ofthe lid for use, which enables sealing between the 100-L resin containerand the lid, is sealed with a caulking agent.

The test result is shown in Table 1.

TABLE 1 1% Hydrochloric Acid 3% Hydrochloric Acid 10% Hydrochloric AcidSolution Solution Solution Elution Time of 24 Hrs In Conc.: 670 ppm InConc.: 680 ppm In Conc.: 680 ppm Elution Time of 48 Hrs In Conc.: 680ppm In Conc.: 685 ppm In Conc.: 685 ppm In Recovering Rate 99% or higher99% or higher 99% or higher

As being apparent from Table 1, a satisfactory In recovering rate,namely 98% or higher, was achieved by the elution treatment for 24 hoursin all the treatments. The recovering rate was determined based on theweight of the waste LCDs and the In-containing rate, and the Inconcentration in hydrochloric acid and amount of hydrochloric acid afterthe treatment.

1. A method of recovering indium from waste liquid crystal displays,comprising: crushing waste liquid crystal displays that contain indiumtin oxide; dissolving the indium tin oxide from the waste liquid crystaldisplays by using acid, thereby producing an indium compositioncontaining solution; flowing the same into a recovering reactor whileadding metal particles of a metal having an ionization tendency largerthan indium into the recovering reactor; fluidizing the metal particles;precipitating indium or indium alloy contained in the indium compositioncontaining solution onto the surface of the metal particles; thenseparating the deposited indium or indium alloy from the metal particlesby a separating means; and isolating and recovering the separated indiumor indium alloy in a solidified form from the liquid component.
 2. Amethod of recovering indium from waste liquid crystal displays accordingto claim 1, wherein the metal particles of the metal having anionization tendency larger than indium are any one of zinc particles andaluminium particles.
 3. A method of recovering indium from waste liquidcrystal displays according to claim 1, wherein the separating means forseparating the indium or indium alloy deposited onto the metal particlescomprises any one of a vibrating means for vibrating the metal particlesby ultrasonic waves and a stirring means for stirring the metalparticles by electromagnet and thereby making the metal particlescollide with one another.
 4. A method of recovering indium from wasteliquid crystal displays according to claim 1, wherein the indiumcomposition-containing solution produced by dissolving the indium tinoxide from the waste liquid crystal displays is flown into an impurityremoving reactor prior to the flowing of the indiumcomposition-containing solution into the recovering reactor; metalparticles of a metal having an ionization tendency larger than animpurity metal other than the indium in the indiumcomposition-containing solution are added into the impurity removingreactor, thereby fluidizing the metal particles and depositing theimpurity metal on the surface of the metal particles; and then thedeposited impurity metal is separated and removed from the metalparticles by the separating means.
 5. A method of recovering indium fromwaste liquid crystal displays according to claim 4, wherein theseparating means for separating the impurity metal deposited onto themetal particles comprises any one of a vibrating means for vibrating themetal particles by ultrasonic waves and a stirring means for stirringthe metal particles by electromagnet and thereby making the metalparticles collide with one another.
 6. A method of recovering indiumfrom waste liquid crystal displays according to claim 4, wherein theimpurity metal is tin.
 7. A method of recovering indium from wasteliquid crystal displays according to claim 4, wherein the metalparticles of the metal having an ionization tendency larger than theimpurity metal are iron particles.
 8. A method of recovering indium fromwaste liquid crystal displays according to claim 7, wherein alkali isadded into the indium composition-containing solution with the impuritymetal removed therefrom, and iron is removed in the form of hydroxide bysedimentation.
 9. A method of recovering indium from waste liquidcrystal displays, comprising: crushing waste liquid crystal liquiddisplays that contain indium tin oxide; dissolving the indium tin oxidefrom the waste liquid crystal displays by using acid, while the crushedwaste liquid crystal displays are kept placed in a bag, therebyproducing an indium composition-containing solution; and washing andneutralizing the waste liquid crystal displays placed in the-bag andthen drying the same.
 10. An apparatus for recovering indium from wasteliquid crystal displays, comprising: a crusher for crushing waste liquidcrystal liquid displays that contain indium tin oxide; an indiumdissolution device for dissolving the indium tin oxide from the wasteliquid crystal displays by using acid, thereby producing an indiumcomposition-containing solution; a recovering reactor for allowing theindium composition-containing solution produced by the indiumdissolution device to flow into the recovering reactor while allowingmetal particles of a metal having an ionization tendency larger thanindium to be added into the recovering reactor, thereby carrying out ametal deposition reaction that deposits indium or indium alloy onto themetal particles; a separating means for separating the deposited indiumor indium alloy from the metal particles to recover the same; and anisolating means for isolating the separated indium or indium alloy in asolidified form from the liquid component.
 11. An apparatus forrecovering indium from waste liquid crystal displays according to claim10, wherein the metal particles of the metal having an ionizationtendency larger than indium are any one of zinc particles and aluminiumparticles.
 12. An apparatus for recovering indium from waste liquidcrystal displays according to claim 10, wherein the separating means forseparating the indium or indium alloy deposited onto the metal particlescomprises any one of a vibrating means for vibrating the metal particlesby ultrasonic waves and a stirring means for stirring the metalparticles by electromagnet and thereby making the metal particlescollide with one another.
 13. An apparatus for recovering indium fromwaste liquid crystal displays according to claim 10, wherein an impurityremoving reactor is disposed on the upstream side of the recoveringreactor, said impurity removing reactor being arranged to flow theindium composition-containing solution produced by the indiumdissolution device into the impurity removing reactor; add metalparticles of a metal having an ionization tendency larger than animpurity metal other than the indium in the indiumcomposition-containing solution into the impurity removing reactor,thereby fluidizing the metal particles and depositing the impurity metalonto the surface of the metal particles; and have a means of separatingand removing the deposited impurity metal from the metal particles. 14.An apparatus for recovering indium from waste liquid crystal displaysaccording to claim 13, wherein the separating means for separating theimpurity metal deposited onto the metal particles comprises any one of avibrating means for vibrating the metal particles by ultrasonic wavesand a stirring means for stirring the metal particles by electromagnet,thereby making the metal particles collide with one another.
 15. Anapparatus for recovering indium from waste liquid crystal displaysaccording to claim 13, wherein the impurity metal is tin.
 16. Anapparatus for recovering indium from waste liquid crystal displaysaccording to claim 13, wherein the metal particles of the metal havingan ionization tendency larger than the impurity metal are ironparticles.
 17. An apparatus for recovering indium from waste liquidcrystal displays according to claim 16, wherein alkali is added into theindium composition-containing solution with the impurity metal removedtherefrom, and iron is removed in the form of hydroxide bysedimentation.